Billionmail/BillionMail · error

rar command not found, please install it first

Error message

rar command not found, please install it first

What it means

RarUnpacker.Compress shells out to the proprietary 'rar' CLI rather than implementing rar compression in Go. Before running, it calls exec.LookPath("rar"); if the binary is not on PATH it returns this error. The rar CLI is not free software and is often absent from containers and CI images.

Source

Thrown at core/internal/service/compress/rar.go:161

			// increase the size of already decompressed file
			return r.incWritten(n)
		}()

		if err != nil {
			return err
		}
	}

	return nil
}

// Compress compresses files or directories into a rar archive using external rar command
func (r *RarUnpacker) Compress(dst string, srcList ...string) error {
	// check if 'rar' command exists
	_, err := exec.LookPath("rar")
	if err != nil {
		return errors.New("rar command not found, please install it first")
	}

	// ensure dst ends with .rar
	if !strings.HasSuffix(strings.ToLower(dst), ".rar") {
		dst += ".rar"
	}

	// get absolute paths to avoid path traversal issues
	dstAbs, err := filepath.Abs(dst)
	if err != nil {
		return err
	}

	// prepare command arguments
	args := []string{"a", "-ep1", "-r"}

	// add destination file
	args = append(args, dstAbs)

View on GitHub (pinned to fc36c76c05)

Solutions

1. Install the rar binary (e.g. apt-get install rar or download from rarlab.com) and ensure it is on PATH
2. Add rar to the Dockerfile of the deployment image
3. Switch to the gzip/zip unpacker if rar format is not strictly required
4. Verify with `which rar` inside the same user/container context that runs the service

Example fix

// Dockerfile before
FROM alpine
// after
FROM alpine
RUN apk add --no-cache unrar && wget -O /usr/local/bin/rar https://www.rarlab.com/rar/rarlinux-x64-*.tar.gz (or apt-get install rar)

if _, err := exec.LookPath("rar"); err != nil {
	return fmt.Errorf("rar is not installed: %w", err)
}

if err := r.Compress(dst, src...); err != nil && strings.Contains(err.Error(), "rar command not found") {
	// fall back to gzip unpacker or surface install instructions to the operator
}

When it happens

Trigger: Calling RarUnpacker.Compress on a machine where the rar executable is not installed or not on PATH (common in slim Docker images, Alpine, CI runners).

Common situations: Deploying to a minimal container that only has unzip/gzip; switching environments where rar was installed manually; PATH differences between dev shell and systemd/docker context.

Related errors

• unrar command not found, please install it first
• disk quota exceeded
• illegal file path:
• source file/directory does not exist: %s
• rar compression failed: %s - %s

AI-assisted analysis of Billionmail/BillionMail@fc36c76c05 (2026-09-05). Data as JSON: /api/errors/376f6532f73b4632. Report an issue: GitHub.